Require assistance in determining whether to alter the gear ratio in your Duramax diesel?

By adjusting the ratio to accommodate larger tires, you can enhance fuel efficiency, reduce EGT temperatures, enhance towing capabilities, and minimize strain on both your transmission and drivetrain.

A pinion with a smaller diameter than the ring gear causes the drive shaft to rotate faster than your axle shafts and wheels. We call this relationship the axle ratio. You'll often see these ratios written as "3.42:1" or described as a "3.42 rear axle." Don't worry if this sounds technical—it simply means the drive shaft and pinion need to turn 3.42 times to make your axle shafts complete one full rotation. This ratio is crucial for your vehicle's performance.

When your drive shaft needs fewer turns to rotate the wheels (such as with a 3.08:1 ratio), this is called a lower numeric axle ratio. These lower ratios can be really helpful for reducing engine strain during highway driving and may improve your fuel economy too. If you find yourself frequently towing heavy loads or if you enjoy more responsive acceleration, you might be happier with a truck that has a higher numeric axle ratio. Just keep in mind that while these higher ratios give you better pulling power for your needs, they typically use more fuel because your engine runs at higher RPMs at the same speed compared to trucks with lower numeric ratios. We're here to help you find the perfect balance for your specific driving requirements.

Pinion Gear Products

Conclusion 

Here is some first hand Knowledge from the Dmaxstore team.

2001-2005 Duramax Trucks with 5 Speed Allison:

2006-2019 Duramax Trucks with 6 Speed Allison: